The invention relates to apparatus and methods for controlling the concentrations of solute in hydrocarbon solvent.
In the several methods of polymerizing aliphatic olefins to solid polymers having high molecular weight, hydrocarbon solvents, such as cyclohexane, are frequently used to facilitate the polymerization reaction and also the subsequent transfer and separation steps. See for example, Hogan, et al., U.S. Pat. No. 2,825,721, Mar. 4, 1958. Several methods of polymer-solvent separation have been developed which include flashing some solvent, for example, such as in Seebold, U.S. Pat. No. 2,475,643, July 12, 1949, or Wallace, U.S. Pat. No. 3,036,057, May 22, 1962, to reach a desired polymer concentration in the solvent before separating the polymer in solvent by further steps. Frequently, the further steps include for example, further flashing, and/or melt devolitilization, for example, utilizing apparatus such as marketed by Werner and Pfleiderer Corporation. Where melt devolitizers are utilized, control of polymer concentration, and flow rates in the melt devolitilizer feed are extremely important.